1. Field of the Invention
The invention relates to transmissions with shifting elements. In particular, the invention relates to automatic transmissions with transmission piston decelerators.
2. Related Art
Transmissions transfer torque between input shafts, powered by engines or motors, and output shafts that drive devices, such as wheels or belts. Within the transmission, transmission pistons provide a means to engage and disengage clutches that transfer torque from one device to another, such as during the transition from one gear ratio to another. During the engagement of the clutch, jerky, shocking motion may occur when rotating clutch plates rapidly make contact with stationary clutch plates.
Traditionally, separator springs have been used to decelerate the pistons before they engage the clutch plates to provide a smoother engagement of the clutch. However, it may be difficult to obtain the correct spring characteristics to help decelerate the piston without compromising on the load and torque transfer requirements. Spring separators also add another component to the clutch assembly. This adds to material and production costs. Additionally, spring separators introduce drag that may inhibit smooth engagement and disengagement of the clutch. Also, software and control calibration may be used to fine tune the engagement, disengagement, and deceleration of the piston. Calibration is time consuming and does not cover all tolerance ranges of the shifting elements. Removing the spring separators simplifies and speeds up the calibration process by eliminating a variable. Thus, there is a need for a transmission piston decelerator that does not require spring separators and reduces the time required for calibration.